High temperature nickel-iron base alloy



Uite rates Patent HIGH TEMPERATURE NICKEL-IRON BASE ALLOY Rudolf H. Thielemann, Palo Alto, Calif., assignor to Sierra Metals Corporation, a corporation of Delaware No Drawing. Filed July 29, 1957, Ser. No. 674,568 Claims. (Cl. 75-171) This invention relates to an iron-nickel base austenitic type metal alloy, and particularly to one such alloy which includes chromium and tungsten, as well as other constituents.

Important features of the iron-nickel base austenitic metal alloyare (1) it possesses high strength at elevated temperatures of the order of 1200 F. to 1500 F.; (2) is readily forgeable at temperatures in the range of from 1950 F. to 2100 F.; (3) is corrosion resistant at temperatures of from 1200 F. to 1500" F.; and (4) is capable of withstanding thermal shock. i

As a result of these markedly improved, superior high temperature properties, the metal alloy of this invention is particularly useful as a wheel 1) in an aircraft gas turbine engine and (2) in a high pressure steam turbine, as well as the material for other parts in all types of engines, such as valve seats, exhaust valves, and the like.

The prior art iron base metal alloys used as wheel material in aircraft gas turbine engines, such as A-286 (14.5

percent of chromium, 26 percent of nickel, 1.25 percent of molybdenum, 2 percent of titanium, 0.3 percent of vanadium, and the balance, essentially iron), are, for all practical purposes, non-utilizable at temperatures of 1200 F. and above since the strength characteristics thereof are too low for use'as wheel material at such elevated temperatures. In contrast, the alloy of this invention maintains its strength characteristics at temperatures up to 1500 -F.,as do also wheels made from this alloy and used in gas turbine engines which wheels are subject to temperatures between 1200 F. and 1500" F. i i

I The iron-nickel base metal alloy of this invention is comprised, by weight of approximately: 10 to 20 percent of chromium, 18 to 50 percent of nickel, 1.5 to 8 percent of tungsten, 1 to 5 percent of columbium, or tantalum, or mixtures thereof, 2 to 4 percent of titanium, 0.05 to 0.25 percent of carbon, and the balance, essentially iron. 1

To achieve the optimum desired properties, the following impurities preferably should be held to the following limits by weight in the alloy. The manganese content in the final alloy should be no more than about 2.0 percent, the silicon content, no more than about 1.0 percent, and the aluminum content, no more than about 0.5

percent.

As will be seen from the examples herein, the strength characteristics at elevated temperatures of the alloy of this invention are improved by the addition of cobalt. I have found that the addition of cobalt in amounts up to 10 percent by weight of the final alloy, preferably 1 'to 10 percent by weight of cobalt, imparts to the alloy metallurgical stability and strength characteristics of the alloy of this invention.

It-is important to note that the maximum amount of boron which may be used in the alloy of this invention is 2,981,621 Patented Apr. 25, 1961.

Example 1 A 5 pound ingot of an iron-nickel base metal alloy composition containing 15 percent of chromium, 27.5 percent of nickel, 3 percent of tungsten, 3 percent of titanium, 3 percent of columbium, 0.1 percent of carbon, and the balance, essentially iron, all by weight, was prepared by melting the iron under a vacuum condition of about 10 microns at a temperature of about 2900 F. and maintaining the iron in a molten condition at this temperature until degassing was complete. Nickel in an amount of 27.5 percent of the total weight ofthe alloy was then added, followed by 15 percent of chromium, 3 percent of tungsten, 3 percent of columbium, 3 percent of titanium, and 0.1 percent of carbon in the form of graphite. The resulting molten metal alloy was cast into an ingot mold and allowed to solidify under vacuum;

It is to be noted that the carbon may be added to the molten mix in the form of columbium carbide or be present in the iron.

Test bars inch diameter and 3 inches long) were fabricated from this ingot by the usual hot working procedure, i.e. forging, at a temperature of between 1950 F. and 2050 F. and then heat treated in air as follows: The test bars were heated to a temperature of about 2000 F., held at this temperature for about 2 hours, cooled in air to room temperature, heated to a temperature of about 1350 F., held at this temperature for about 16 hours, and their air cooled to room temperature.

The fabricated, heat treated test bars hada yield strength at 0.2 percent offset of (i) 141,000 p.s.i. at room temperature, and (ii) 115,000 p.s.i. at a temperature of about 1300 F.

At a temperature of about 1300 F. in air and under a load of 70,000 p.s.i., the rupture life of these test bars was in excess of hours.

Example 2 A 5 pound ingot of an iron-nickel base metal alloy composition containing 15 percent of chromium, 27.5 percent of nickel, 3 percent of tungsten, 3 percent of titanium, 3 percent of columbium, 5 percent of cobalt, 0.1 percent of carbon, and the balance, essentially iron, all by weight, was prepared in the same manner as set forth in Example 1, with the exception that the 5 percent of cobalt was added to the iron melt in addition to the constituents of the alloy of Example 1. w

Test bars 4 inch diameter and 3 incheslong) were fabricated from the ingot of this example and heat treated in the same manner as set forth in Example 1. The fabricated, heat treated test bars of this example had a yield strength at 0.2 percent oltset of (i) 150,000 p.s.i. at room temperature and (ii) 125,000 p.s.i. at a temperature of about 1300 F.

At a temperature of about 1300 F. in air and under a load of 70,000 p.s.i., the rupture life of these bars was in excess of 100 hours.

Example 3 A 5 pound ingot of an iron-nickel base metal alloy composition containing 15 percent of chromium, 27.5 percent of nickel, 3 percent of tungsten, 3 percent of titanium, 3 percent of columbium, 5 percent of cobalt, 0.2 percent of zirconium, 0.015 percent of boron, 0.1 percent of carbon, and the balance, essentially iron, all by fabricated from the ingot of this example and heat treated in the same manner as set forth in Example 1. The fabricated, heat treated test bars of this example had a yield strength at 0.2 percent offset of (i) 150,000 p.s.i. at room temperature and (ii) 125,000 p.s.i. at a temperature of about 1300" F;

At a temperature of about 1300 F. in air and under a load of 70,000 p.s.i., the rupture life of the test bars of this example was in excess of 100 hours.

The workability of the test bars of this example was much better than the workability of the test bars of Examples 1 and 2. This is due to the incorporation of zirconium and boron in the alloy of this example.

Example 4 A 5 pound ingot of an iron-nickel base metal alloy composition containing percent of chromium, 18 percent of nickel, 1.5 percent of tungsten, 4 percent of titanium, 1 percent of tantalum, 0.25 percent of carbon, and the balance, essentially iron, all by weight, was prepared in the same manner as set forth in Example 1.

Test bars (A inch diameter and 3 inches long) were fabricated from the ingot of this example and heat A 5 pound ingot of an iron-nickel base metal alloy composition containing 10 percent of chromium, 18 percent of nickel, 1.5 percent of tungsten, 4 percent of titanium, 1 percent of columbium, 10 percent of cobalt, 0.1 percent of carbon, and the balance, essentially iron, all by weight, was prepared in the same manner as set forth in Example 1, with the exception that the 10 percent of cobalt was added to the iron melt in addition to the constituents of the alloy of Example 1.

Test bars A inch diameter and 3 inches long) were fabricated from the ingot of this example and heat treated in the same manner as set forth in Example 1.

The fabricated, heat treated test bars of this example had a yield strength at 0.2 percent olfset of (i) 145,000 p.s.i. at room temperature and (ii) 122,000 p.s.i. at a temperature of about 1300 F.

At a temperature of'about 1300 F. in air and under a load of 70,000 p.s.i., the rupture life of these test bars was in excess of 100 hours.

7 Example 6 A 5 pound ingot of an iron-nickel base metal alloy composition containing 10 percent of chromium, 18 percent of nickel, 1.5 percent of tungsten, 4 percent of titanium, 1 percent of columbium, 5 percent of cobalt, 0.2 percent of zirconium, 0.015 percent of boron, 0.1 per- .cent of carbon, and the balance, essentially iron, all by weight, was prepared in the same manner as set forth in Example 1, with the exception that the above proportions of cobalt, zirconium and boron were added to the iron melt in addition to the constituents of the alloy of Example 1.

Test bars inch diameter and 3 inches long) were fabricated from the ingot of this example and heat --treated in the same manner as set forth in Example 1. "The fabricated, heat treated test bars of this example had a yield strength at 0.2 percent offset of (i) 148,000 p.s.i. at room temperature and (ii) 125,000 p.s.i. at a temperature of about 1300 F. N

The rupture life of these test bars at a temperature of about 1300" F. in air and under a load of 70,000 p.s.i. was in excess of hours.

Example 7 A 5 pound ingot of an iron-nickel base metal alloy composition containing 10 percent of chromium, 50 percent of nickel, 8 percent of tungsten, 3.5 percent of titanium, 5 percent of columbium, 0.1 percent carbon, and the balance, essentially iron, all by weight, was prepared in the same manner as set forth in Example '1.

Test bars (A inch diameter and 3 inches long) were fabricated from the ingot of this example and heat treated in the same manner as set forth in Example 1. The fabricated, heat treated test bars of this example had a yield strength at 0.2 percent offset of (i) 152,000 p.s.i. at room temperature and (ii) 127,000 p.s.i. at a temperature of about 1300 F.

At a temperature of about 1300 F. in air and under a load of 65,000 p.s.i., the rupture life of these test bars was in excess of 100 hours.

Example 8 A 5 pound ingot of an iron-nickel base metal alloy composition containing 10 percent of chromium, 50 percent of nickel, 8 percent of tungsten, 3.5 percent of titanium, 5 percent of tantalum, 5 percent of cobalt, 0.1 percent of carbon, and the balance, essentially iron, all by weight, was prepared in the same manner as set forth in Example 1, with the exception that the 5 percent of cobalt was added to the iron melt in addition to the constituents of the alloy of Example 1.

Test bars inch diameter and 3 inches long) were fabricated from the ingot of this example and heat treated in the same manner as set forth in Example 1. The fabricated, heat treated test bars of this example had a yield strength at 0.2 percent offset of (i) 156,000 p.s.i.

at room temperature and (ii) 129,000 at a temperature of about 1300 F.

The rupture life of these test bars at a temperature of about 1300 F. in air and under a load of 70,000 p.s.i. was in excess of 100 hours.

Example 9 A 5 pound ingot of an iron-nickel base metal alloy composition containing 10 percent of chromium, 50 percent of nickel, 8 percent of tungsten, 3.5 percent of titanium, 5 percent of columbium, 5 percent of cobalt, 0.2 percent of zirconium, 0.015 percent of boron, 0.1 percent of carbon, and the balance, essentially iron, all by weight, was prepared in the same manner as set forth in Example 1, with the exception that the above proportions of cobalt, zirconium and boron were added to the iron melt in addition to the constituents of the alloy of Example 1.

Test bars inch diameter and 3 inches long) were fabricated from the ingot of this example and heat treated in the same manner as set forth in Example 1. The

fabricated, heat treated test bars of this example had a yield strength at 0.2 percent offset of (i) 156,000 p.s.i. at room temperature and (ii) 130,000 p.s.i. at a temperature of about 1300.F.

The rupture life of these test bars at a temperature of about 1300 F. in air under a load of 70,000 p.s.i. was in excess of 100 hours.

Example 10 A 5 pound ingot of an iron-nickel base metal alloy composition containing 15 percent of chromium, 27.5 percent of nickel, 3 percent of tungsten, 3 percent of titanium, 3 percent of columbium, *1 percent of cobalt, 10.2. percent of carbon, and the 'balance,..essentially iron.

' V all by weight, was prepared in the same manner as set forth in Example 1, with the exception that the 1 percent of cobalt was added to the iron melt in addition to the constituents of the alloy of Example 1.

Test bars inch diameter and 3 inches long) were fabricated from the ingot of this example and heat treated in the same manner as set forth in Example 1. The fabricated, heat treated test bars of this example had a yield strength at 0.2 percent ofiset of (i) 142,000 p.s.i. at room temperature and (ii) 117,000 p.s.i. at a temperature of about 1300 F.

The rupture life of these test bars at a temperature of about 1300 F, in air under a load of 70,000 p.s.i. was in excess of 100 hours.

Example 11 A 5 pound ingot of an iron-nickel base metal alloy composition containing 15 percent of chromium, 27.5 percent of nickel, 3 percent of tungsten, 2 percent of titanium, 3 percent of tantalum, 5 percent of cobalt, 0.3 percent of zirconium, 0.1 percent of boron, 0.05 percent of carbon, and the balance, essentially iron, all by weight, was prepared in the same manner as set forth in Example 1, with the exception that the above proportions of cobalt, zirconium and boron were added to the iron melt in addition to the constituents of the alloy of Example 1.

Test bars inch diameter and 3 inches long) were fabricated from the ingot of this example and heat treated in the same manner as set forth in Example 1. The fabricated, heat treated test bars of this example had a yield strength at 0.2 percent ofiset of (i) 152,000 p.s.i. at room temperature and (ii) 127,000 p.s.i. at a temperature of about 1300 F.

The rupture life of these test bars at a temperature of about 1300 F. in air under a load of 70,000 p.s.i. was in excess of 100 hours.

Example 12 A 5 pound ingot of an iron-nickel base metal alloy composition containing 15 percent of chromium, 27.5 percent of nickel, 3 percent of tungsten, 3 percent of titanium, 3 percent of columbium, 5 percent of cobalt, 0.4 percent of zirconium, 0.015 percent of boron, 0.1 percent of carbon, and the balance, essentially iron, all by weight, was prepared in the same manner as set forth in Example 1, with the exception that the above proportions of cobalt, zirconium and boron were added to the iron melt in addition to the constituents of Example 1.

In attempting to fabricate test bars A inch diameter and 3 inches long from the ingot of this example, the bars cracked and could not be worked under hot working conditions.

The above detailed description of this invention has been given for clearness of understanding only. No unnecessary limitations should be understood therefrom, as modifications will be obvious to those skilled in the art.

I claim:

1. A metal alloy consisting essentially of, by weight: 10 to 20 percent chromium; 18 to 50 percent nickel; 1.5 to 8 percent tungsten; 1 to 5 percent of a metal of the class consisting of columbium, tantalum and mixtures thereof; 2 to 4 percent titanium; 0.05 to 0.25 percent carbon; and the balance, iron.

2. A metal alloy consisting essentially of, by weight: 10 to 20 percent chromium; 18 to 50 percent nickel; 1.5 to 8 percent tungsten; 1 to ,5 percent columbium; 2 to 4 percent titanium; 0.05 to 0.25 percent carbon; and the balance, iron.

3. A metal alloy consisting essentially of, by weight: 10 to 20 percent chromium; 18 to 50 percent nickel; 1.5 to 8 percent tungsten; 1 to 5 percent tantalum; 2 to 4 percent titanium; 0.05 to 0.25 percent carbon; and the balance, iron.

to 8 percent tungsten;'1 to 5 percent of a metal of the class consisting of columbium, tantalum and mixtures thereof; 2 to 4 percent titanium; 0.05 to 0.25 percent carbon; boron in an amount up to 0.1 percent; zirconium in an amount up to 0.3 percent; and the balance, iron.

6. A meat alloy consisting essentially of, by weight: 10 to 20 percent chromium; 18 to 50 percent nickel; 1.5 to 8 percent tungsten; 1 to 5 percent of a metal of the class consisting of columbium, tantalum and mixtures thereof; 2 to 4 percent titanium; 0.05 to 0.25 percent carbon; cobalt in an amount up to 10 percent; boron in an amount up to 0.1 percent; zirconium in. an amount up to 0.03 percent; and the balance, iron.

, 7. A metal alloy consisting essentially of, by weight: 10 to 20 percent chromium; 18 to 50 percent nickel; 1.5 to 8 percent tungsten; 1 to 5 percent columbium; 2 to 4 percent titanium; 0.05 to 0.25 percent carbon; cobalt in an amount up to 10 percent; boron in an amount up to 0.1 percent; zirconium in an amount up to 0.3 percent; and the balance, iron.

8. A metal alloy consisting essentially of, by weight: 10 to 20 percent chromium; 18 to 50 percent nickel; 1.5 to 8 percent tungsten; l to 5 percent tantalum; 2 to 4 percent titanium; 0.05 to 0.25 percent carbon; cobalt in an amount'up to 10 percent; boron in an amount up to 0.1 percent; zirconium in an amount up to 0.3 percent; and the balance, iron.

9. A metal alloy consisting essentially of, by weight: 15 percent chromium; 27.5 percent nickel; 3 percent tungsten; 3 percent titanium; 3 percent of a metal of the class consisting of columbium, tantalum and mixtures thereof; 0.1 percent carbon; 5 percent cobalt; and the balance, iron.

10. A metal alloy consisting essentially of, by weight:

15 percent chromium; 27.5 percent nickel; 3 percent References Cited in the file of this patent UNITED STATES PATENTS 2,432,619 Franks et al. Dec. 16, 1947 2,460,817 Fisher Feb. 8, 1949 2,513,467 Franks et a1. July 4, 1950 2,513,469 Franks et al. July 4, 1950 2,519,406 Scott et al Aug. 22, 1950 2,587,275 Bash Feb. 26, 1952 2,590,835 Kirkby et a1 Apr. 1, 1952 2,704,250 Payson Mar. 15, 1955 2,742,356 Prasse et al. Apr. 17, 1956 2,777,766 7 Binder Jan. 15, 1957 FOREIGN PATENTS 785,271 Great Britain Oct. 23, 1957 OTHER REFERENCES Pages 8 and 9 of Specific interest. 

1. A METAL ALLOY CONSISTING ESSENTIALLY OF, BY WEIGHT: 10 TO 20 PERCENT CHROMIUM; 18 TO 50 PERCENT NICKEL; 1.5 TO 8 PERCENT TUNGSTEN; 1 TO 5 PERCENT OF A METAL OF THE CLASS CONSISTING OF COLUMBIUM, TANTALUM AND MIXTURES THEREOF; 2 TO 4 PERCENT TITANIUM; 0.5 TO 0.25 PERCENT CARBON; AND THE BALANCE, IRON. 